1. Field of the Invention
The present invention relates to a method for configuring and managing a multicast tree in a wireless ad-hoc network and a multicast data delivery system using the same and, more particularly, but not exclusively, to a method for configuring an efficient multicast tree, a method for optimizing the multicast tree, and a multicast system using the methods.
2. Discussion of the Related Art
A mobile ad-hoc network (MANET) is capable of being auto-configured by mobile nodes without the aid of an infra-structure. For this reason, the MANET has attracted much attention as an underlying network for supporting ubiquitous computing environments and can be effectively applied not only to networking systems under special circumstances, for example, military operations and disaster areas, but also to community-based group communications, for example, network games and conferences.
A large amount of research has been conducted on applying a multicast system, which is an efficient transmission unit for group communication, to the MANET. However, since the MANET has restrictions, such as limited wireless communication resources and limited energy capacities of the mobile nodes, the restrictions need to be fully considered in order to apply multicast mechanism to the MANET.
Multicasting methods proposed to overcome the restrictions may be classified into a multicasting method provided in a network layer and a multicasting method provided in an application layer.
According to the network-layer multicasting method, all nodes of a network must manage the status of multicasting. In contrast, according to the application-layer multicasting method in which a virtual path is overlaid on an actual path, non-member nodes on a path relay multicast data, like unicast routers, without managing the status of multicasting. Accordingly, the latter method is much more efficient than the former method when there are many groups, nodes are very mobile, or a network undergoes big changes in membership.
However, since now known application-layer multicasting methods cannot sufficiently reflect actual physical network structures in generation of a virtual path, it is necessary to minimize redundant packet forwarding.